This invention relates to a video format signal recording/reproducing system which employs a recording medium such as a video disc.
The so-called video format signal has a composition similar to a normal TV signal, comprising an information signal part which bears information (video information normally), and a horizontal/vertical synchronizing signal part, with a field signal consisting of a horizontal/vertical blanking part and the following information signal, and normally a pair of consecutive field signals forming one frame signal.
It is generally known to record a video format signal on a recording medium such as a video disc or video tape after FM modulation and then reproduce the video format signal at a desired time and place. In such a recording/reproducing system, it is also generally known to form a video frame including an image frame representing video information and a voice frame representing voice information and to insert the voice frame via time base compression into the information signal part of the video frame signal for recording and reproducing, so as to obtain an audio accompaniment corresponding to a reproduced stationary image.
However, in a recording/reproducing system for stationary images with voice accompaniment as described, it is necessary that the voice information be identified as to whether it is monaural, stereo or bilingual so that it is possible in voice reproduction to obtain not only a monaural audio portion but also stereo or bilingual (two-language).
In general, the composite video format signal will comprise a series of information signal portions separated by vertical blanking intervals. If a particular information signal portion will include video, or image, information, an image frame identification signal will be inserted into the immediately preceding vertical blanking interval. Alternatively, if the information signal portion will include voice, or audio, information, a voice frame identification signal will be inserted into the immediately preceding vertical blanking interval.
After FM modulation, the series of information and blanking intervals will be recorded onto a rotating video disc typically having a spiral track thereon. As the disc rotates, the image frame and voice frame portions of the video signal will be recorded at successive positions along the recording track.
Upon reproduction, the reproduction circuitry examines each vertical blanking interval to determine whether the next information signal is to be supplied to a video display or an audio processing circuit. The reproduced image is a stationary image so that the interruption in the flow of video information when an audio information portion is received will not detract from the display. A problem arises, however, if the reproduction circuitry must determine whether the sound represented by the received voice information signal is stereo, bilingual or monaural.